Conventional sign supports for retaining signs in viewing positions along roads and highways comprise stationary posts and frames attached to the road shoulder or ground adjacent the road and portable sign supports. Portable sign supports include foldable A frames and inverted T frames. The conventional inverted T frame sign support has a pair of frames connected to perforated upright members. Plywood or aluminum work zone or road condition signs are fastened with bolts to the upright members. Each frame has a horizontal leg member and an upright stud or receiver secured to the center of the leg member. The studs are short having a height of no more than 12 inches. A small section of the upright member telescoped over the stud is attached to the stud with a reasonable connection. The upright member and stud are separable to facilitate handling, storage, and transport. The stud is located below the automobile impact area on the upright member. When the upright members are hit with an automobile, substantial impact forms on the upright members bend and break the studs from the horizontal members and bend, break and fragmentize the upright member. The separated parts of the sign and support frame can penetrate the windshield of the automobile or enter the bottom of the driving compartment which can cause injury to persons and property.
United States Transportation Equity Act, Public Law 105-178, requires mandatory compliance with sign safety guidelines. All highway appurtances and devices, including signs, guard rails, barricades, and traffic cones, to be tested for crashworthiness. The test involves crashing a small automobile into each device at 100 km/hour. A device is considered safe or crashworthy if none of its components penetrate in the test automobile's passenger compartment via the windshield or up through the floorboards. The automobile must also remain on its pre-crash trajectory and not experience unnecessary deceleration. A number of tests have been conducted on the conventional sign and sign support to ascertain crashworthy structures. The results of these tests have not been favorable. The portable sign systems often found crashworthy are those that display flexible rollup traffic signs. W. A. Werner in U.S. Pat. No. 4,951,407 discloses a yieldable sign stand. There is a high cost of converting entire inventories of connected sign systems over to rollup sign systems. Sign systems have been proposed with structures that break away at their base or horizontal member with the intent of allowing the sign and a portion of the upright members to pass over the automobile. The type of controlled fracture structure tends to direct the sign into the windshield of the automobile or send the sign spinning into on-coming traffic.